Which antibody class is known for its ability to cross the placenta?

The antibody class known for its ability to cross the placenta is IgG. This is critical during pregnancy because IgG provides passive immunity to the fetus. The placenta acts as a barrier that selectively allows certain antibodies, particularly IgG, to pass through from the mother to the developing fetus, thereby offering protection against infections during the early stages of life when the baby's own immune system is not fully developed.

IgG's structural characteristics facilitate this transfer; it is the only antibody class that can exploit placental transport mechanisms. Once transferred, IgG can help protect the newborn from pathogens by neutralizing toxins and viruses and facilitating opsonization, which enhances phagocytosis.

Understanding the properties and functions of the different antibody classes is important in immunology and helps inform practices related to maternal and child health, particularly in contexts where the mother may be exposed to infections that can impact fetal development.